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961.
We have performed a rather extensive microscopic calculation of the 17F-17O Coulomb energy differences ΔEC. Our main purpose has been to study the effects of (i) folded diagrams, (ii) core polarization and (iii) the effects due to different nucleon-nucleon potentials, different single-particle spectra and different radial wave functions. Using a proton-neutron representation we have included higher-order Coulomb corrections like e.g. the coupling of valence particles to collective vibrations of the core.The inclusion of folded diagrams is very important; it is equivalent to a self-consistent treatment of the Q-box starting energies. It causes a significant suppression of the effect due to core polarization, its contribution to ΔEC becoming small, about 0.03 MeV. As a consequence of this “self-correcting” behavior our results for ΔEC are quite stable with respect to the choice of different single-particle spectra. Two rather different nucleon-nucleon potentials, the Reid soft-core potential and a meson exchange potential of the Bonn-Jülich group also lead to quite similar results for ΔEC. In the case of , for example, ΔC calculated with the Reid potential ranges, depending on other assumptions, from 3.36 to 3.43 MeV and from 3.36 to 3.40 MeV with the Bonn-Jülich potential: Both are significantly smaller than the experimental value of 3.54 MeV. Optimizing the radial wave functions in the spirit of a Brueckner-Hartree-Fock theory improves the calculated values of ΔEC for the state but not for .We feel that other processes such as the explicit inclusion of core deformation or mesonic degrees of freedom or both are needed to explain the Coulomb displacement energies. 相似文献
962.
The theorem of B. Segre mentioned in the title states that a complete arc of PG(2,q),q even which is not a hyperoval consists of at mostq−√q+1 points. In the first part of our paper we prove this theorem to be sharp forq=s
2 by constructing completeq−√q+1-arcs. Our construction is based on the cyclic partition of PG(2,q) into disjoint Baer-subplanes. (See Bruck [1]). In his paper [5] Kestenband constructed a class of (q−√q+1)-arcs but he did not prove their completeness. In the second part of our paper we discuss the connections between Kestenband’s
and our constructions. We prove that these constructions result in isomorphic (q−√q+1)-arcs. The proof of this isomorphism is based on the existence of a traceorthogonal normal basis in GF(q
3) over GF(q), and on a representation of GF(q)3 in GF(q
3)3 indicated in Jamison [4]. 相似文献
963.
964.
965.
Moon Fuk Chan Guansan Chen M. Süleyman Demokan Hwa Yaw Tam 《Optics and Lasers in Engineering》1998,30(1):17-24
The theory and experimental verification of an optical current sensor based on an extrinsic Sagnac interferometer configuration is presented. Superior performance with regard to current sensitivity and input/output linearity, and simple installability of the sensor makes it very suitable for remote current sensing in power distribution applications. 相似文献
966.
A comparison of complete global optimization solvers 总被引:2,自引:0,他引:2
Arnold Neumaier Oleg Shcherbina Waltraud Huyer Tamás Vinkó 《Mathematical Programming》2005,103(2):335-356
Results are reported of testing a number of existing state of the art solvers for global constrained optimization and constraint satisfaction on a set of over 1000 test problems in up to 1000 variables, collected from the literature.The test problems are available online in AMPL and were translated into the input formats of the various solvers using routines from the COCONUT environment. These translators are available online, too. 相似文献
967.
Let K1 and K2 be solid cones in Rn and Rm respectively, and let A be a linear operator such that AK1?K2. Necessary and sufficient conditions for the existence of various kinds of generalized inverses of A taking K2 into K1 are given. Projections which belong to π(K), the set of all linear operators that preserve a are studied. In particular, it is proved that a projection P in π(K) is a simplicial nonnegative linear combination of its rank-one operators iff Im P∩K is a simplical cone. An open question of Burns, Fiedler, and Haynsworth concerning minimal generating matrices of polyhedral cones is also extended and answered affirmatively. 相似文献
968.
C.K.W. Tam 《Journal of sound and vibration》1976,49(3):353-364
A theoretical study of the acoustic modes of a two-dimensional rectangular cavity is presented in this paper. It is found that for cavities with length to depth ratio of unity or larger the natural modes are heavily damped due to acoustic radiation. Numerical results for lower order modes are given. The physical significance of strong radiation damping on the onset of cavity tones induced by outside flow at low Mach number is discussed. 相似文献
969.
Starting from the normal cyano-acetate derivative 3b, obtained from the allo stereoisomer 3a via an unusual epimerization,1 the stereoselective totalsynthesis of (±)-dihydrocorynantheine (1a) was accomplished. 相似文献
970.
A real space renormalization group is formulated for continuum (off-lattice) percolation problems. It is applied to the system of overlapping discs with a variety of distributions of disc radii. Monte Carlo method is used for obtaining recursion relations. The results support universality: The Harris criterion seems to work for percolation. The position of the critical point shows stability against introducing a distribution in the disc radii.Supported in part by SFB 125 Aachen-Jülich-Köln 相似文献